I've just read Kevin Lippert's "War Plan Red: The United States' Secret Plan to Invade Canada and Canada's Secret Plan to Invade the United States." Lippert gave a talk on C-Span which amounted to reading parts of his book aloud, and I was so entertained that I borrowed it from the library. Lippert's scope is broader than his title - he covers U.S./Canadian relations from the War of 1812 (apparently a comedy of errors) to the present - but it focuses on these actual war plans which were developed in the 1920s and 1930s.

As a sample, here's part of the chapter titled "The Pig Heard Round the World":

Kevin Lippert wrote:In June 1859, an American farmer-squatter, Lyman Cutlar, saw a large black pig rooting around in his garden, eating potatoes. He promptly chased, shot, and killed the pig, which turned out to be owned by Charles Griffin, manager of a ranch owned by the imperialist British supermerchant-squatter the Hudson's Bay Company, also the owners of most of Western Canada.

The ensuing fight over liability and compensation quickly escalated into a military standoff. Following the orders of the local US Army commander, Anglophobe Brigadier General William Selby Harney, Oregon landed 66 soldiers under Captain George Pickett (later leader of the ill-fated Pickett's Charge) just north of the Hudson's Bay ranch in late July, transported there by the US warship USS Massachussetts, with its eight 32-pound cannons. The British immediately anchored three warships in Griffin Bay to keep the Americans from occupying the islands.

Both sides upped their positions in rapid succession, and by the end of the summer, Pickett had almost five hundred soldiers with fourteen artillery cannons, while the British increased their force to five warships with more than two thousand men and seventy cannons (echoes of the lopsided Falkland Islands buildup centuries later). With the clear military advantage, the governor of Vancouver Island ordered the British to land and engage the Americans, but Rear Admiral Robert Baynes refused, saying that "to engage two great nations in a war over a squabble about a pig" was foolish... The British finally withdrew their troops in 1872, the Americans in 1874...

In spite of all the saber rattling, no shots were fired and the "war" ended peacefully, which leads at least one historian to call the Pig War "the most perfect war in history." To be accurate, though, one shot was fired and one life lost, that of the anonymous pig.